The present invention relates to a vacuum plasma processing apparatus and method used in processing a semiconductor wafer or a liquid crystal display substrate, etc. by way of dry etching, CVD, sputtering, or other kinds of surface treatment.
A conventional vacuum plasma processing apparatus will be described by way of example.
The constitution of the apparatus is shown in FIGS. 21 and 22. In FIG. 21, a susceptor 3 for holding a to-be-processed board 2 is disposed in a vacuum processing container 1 which has a reaction gas feed port 7 and a vacuum pump 8. An RF generator 4 is connected to the susceptor 3. A cylindrical electrode 5 arranged above the susceptor 3 is connected to an RF generator 6. Specifically, the cylindrical electrode 5 is divided or split to three parts, and three parts are connected to the corresponding RF generators 6 of every 120.degree. or so different phases.
The operation of the apparatus will now be described.
While the gas in the container is discharged from the container 1 by the vacuum pump 8, a reaction gas is introduced into the container 1 from the feed port 7 to bring about plasma. The reaction gas in the container is kept at a suitable pressure. RF powers of phases approximately 120.degree. different each other are applied from the RF generators 6 to the split three parts of the electrode 5, whereby an electric field is formed in the container 1. As a result, plasma is generated because of the acceleration of electrons by the electric field. The to-be-processed board 2 is accordingly surface-treated in the vacuum plasma processing apparatus.
At the same time, the energy of ions entering the to-be-processed board 2 is controllable in the apparatus as the RF generator 4 impresses an RF power to the susceptor 3.
In the conventional structure as above, the intensity of the plasma is large in the vicinity of the electrode 5, whereas the intensity becomes small as it is closer to the center of the container 1. Therefore, the etching speed and the forming speed of a film on the substrate 2 become irregular, turning the apparatus unfit to process particularly a substrate of a large area.